Air impeller device



March 3, 1942. RQSSKQPF 2,274,743

AIR IMPELLER DEVICE Filed April 17, 1939 Patented Mar. 3, 1942 2,274,743v AIR IMPELLER DEVICE Hans Rosskopf, Berlin-Charlottenburg, Germany,

assignor to Brandenburgische Motorenwerke Gesellschaft mit beschrankterHaftung', Berlin- Spandau, Germany, a corporationof Germany ApplicationApril 17, 1939, Serial No. 268,213 In Germany April 25, 1938 4 Claims.(01.123-171) This invention relates to a cooling arrange ment forair-cooled radial aero-engines.

The natural cooling of an air-cooled aeroengine is no longer suificientto meet the exacting requirements of modern aircraft with respect toreducing the surface resistance and increasing the power output. Theair-cooled engines therefore have been provided with blowers for forcedcooling. It appears preferable, as a rule, to arrange a single blowersuflicient for furnishing the entire amount of cooling air on the mainshaft of the engine rather than employing a plurality of such blowers.It has been proposed to arrange such a single blower behind the engine,i. e. at the side away from the propeller, or in front of the engine.While both arrange ments are advantageous to a certain extent, theypresent nevertheless relatively great drawbacks. When arranging the fanbehind the engine, difliculties are encountered in that the air producedby the fan must flow in a direction opposite to the direction of flight.For this reason the cooling air must be constrained to flow throughdefinitely given passages so that the.

construction and the mounting of the engine are dependent upon themanner in which the air is to be directed. Furthermore, the auxiliarycooling apparatus must wholly or in part be displaced towards thepropeller, and a number of other difficulties arise affecting, forinstance, the suspension of the engine and the mounting of the engine inthe nacelle.

The arrangement of the blower in front of the engine is more favorablein this respect. The auxiliary apparatus, as has hitherto been the case,may be arranged behind the engine; the suspension of the engine is notaffected; the

conduits, struts, rods and the like may easily peller is farther awayfrom the engine'to accommodate the blower therebetween. Particularlygreat difficulties are encountered if the propeller is of the variablepitch type, since the accessibility of the adjusting devices is rendereddifficult by the blower lying between propeller and engine. If, on theother hand, the blower is arranged in. front of the propeller, noessential alteration in the conventional construction of the completeengine set is necessary. The relative arrangement of motor and propellerremains as is usual; the auxiliary apparatus and devices may be arrangedin the most suitable way without affecting the arrangement of theconduits and rods; the cooling air may be supplied and carried off in asimple and favorable manner; the impact pressure may be utilized to thefull extent; and in certain cases even a slight increase in thepropelling force may be obtained by the blower. The bearings may bedesigned in a simple and oil-tight manner; the blower may easily beregulated, if desired, in dependence uponthe regulation of the propellerpitch. Unfortunately, however, these advantages are outweighed by afunctional inefficiency of the known frontal blower arrangements asregards their main cooling operation. This deficiency is caused by thefact thatdue to the relatively large distance of the blower from theengine blower is located inside the sectional area of inlet of thiscowl. Particularly favorable con-' ditions of flow are attained if guideblades for 'the air delivered by the blower are provided inside thecowl.

According to another feature of the invention, the blower is driven bythe revolving propeller with the aid of a reduction gear having one ofits members supported on the stationary gear housing. It is alsopossible to utilize the relative speed between the propeller shaft andthe crank shaft for driving the blower. To this end a stationary toothedrim may be secured in the gear housing, one or more intermediate shaftsmounted on the propeller hub being in engagement with the toothed rim.However, since a particular design of the propeller is necessary forthis purpose and since also the oil-tight casing is not so simple toconstruct, it is, as a rule, easier to utilize the relative speedbetween the propeller shaft and crank shaft.

- Figs. 1 and 2 of the accompanying drawing illustrate two embodimentsof the invention in sectional elevation. The arrangement of the blowerand of its drive is substantially the same in both cases, only themanner in which the flow of air is guided being diflerent. Each figureshows an aero-engine having a plurality of radially extending cylindersi8 whose pistons,

not shown, cooperate with the crank shaft I. This crank shaft drives adrum 2 having an internal gearing meshing with a plurality of planetarypinions 3 of which only one is shown. These pinions mesh with astationary sun wheel I and are carried by studs 5 fixed on the propellershaft 6. The propeller I is mounted on the shaft 6. A revolvinginternally toothed rim 8 meshing with planetary pinions 9 (of which onlyone is shown) is also mounted on the propeller shaft 6. Pinions 9 arecarried by individual pins ID mounted on a resilient extension.

Ii of the crank shaft l, i. e. on the bell-shaped portion l2. Pinions 9mesh with the small gear III of the driving shaft H for the fan wheel l5of the blower arrangement. The speed of this wheel is thereforedetermined by the relative speed between the crank shaft I and itsextension II and the propeller driving shaft 6. As shown in the drawing,the fan wheel i5 is mounted in front of the propeller 1 inside the cowli1 revolving together with the propeller. At the entrance of cowl I! andimmediately behind the fan blades iii are mounted inwardly radiatingguide vanes i6 for the air delivered by the blades. Theair thereforereaches in Fig. 1 the fan wheel I 5 with the full impact pressure and issupplied to the interior of the cowl I! through the guide vanes i6 andthus to the cylinders i8 which are located in the rear cowl portion.

As apparent from the drawing, the construction of the engine is notmaterially altered in this novel arrangement. The displacement of thecenter of gravity is slight, since the overhanging masses added to thepropeller are small.

The arrangement according to Fig. 2 shows another possibility ofcontrolling the flow of air insofar as the air is directed by the guidesurfaces is first over the lower cylinder portion and then reverses itsdirection of flow as shown by the curved arrow at the cylinder I 8,flowing over the cylinder head and to escape in the neighborhood of thepropeller through an annular gap 20 disposed at a point where a lowpressure exists owing to known phenomena so that thereby the forcedcirculation of air is influenced in a favorable manner.

What is claimed -is:-

1. In an air-impeller device for aircraft having a propeller, incombination, a rotary airguiding cowl coaxial with said propeller, saidcowl being connected with said propeller so as to rotate therewith, ablower disposed in front of and coaxial with said propeller, said blowerbeing arranged near the inlet opening of said cowl, and driving meansfor actuating said propeller and blower, said means comprising a gearfor imparting to said blower a rotary speed higher than that of saidpropeller.

2. In an air-impeller device for aircraft having a propeller, incombination, an air-guiding annular cowl coaxial with said propeller andhaving a cross section gradually increasing from a frontal inletopening, said cowl being arranged to rotate with said propeller andhaving lateral openings passed through by the blades of said propeller,a blower of propeller type disposed in front of and coaxial with saidpropeller, said blower being rotatable relative to said propeller andarranged in the inlet opening of said cowl, and a transmission gearoperatively connecting said blower with said propeller so as to rotatesaid'blower with a speed higher than that of said propeller.

3. In an air-impeller devic for aircraft having a propeller and meansfor driving'the. propeller comprising a coaxial shaft, in combination, ablower arrangement comprising a fan having a small diameter as comparedwith that of said propeller and being arranged in front of and coaxialwith said propeller, and cowlshaped means for guiding the air from saidblower past said propeller, a reduction gear coupling said shaft withsaid propeller, and a planetary transmission gear having two of itscoacting gear members connected with said shaft and said propeller andits third member connected with said fan to rotate it with a speeddepending upon the relative speed between said propeller and said shaft.

4. In an air-impeller device for aircraft having a propeller and meansfor driving the pro-, peller comprising a coaxial shaft, in combination,a blower arrangement comprising a fan having a small diameter ascompared with that of said propeller and' being arranged in front of andcoaxial with said propeller, and cowlshaped means for guiding the airfrom said blower past said propeller, a reduction. gear coupling saidshaft with said propeller, a resilient extension connected with andarranged coaxial to said shaft, a planetary transmission gear having asun wheel connected with said fan, a concentric internally toothed gearconnected with said propeller and a planetary pinion carrier connectedwith said resilient extension so as to rotate said fan with a speeddepending upon the relative speed of said propeller and said extension.

HANS ROSSKOPF.

